Paleozoic Life and Cambrian Fauna

Paleozoic Life

• The Great Oxygenation event occurred 2.4 billion years ago
• The Cambrian Explosion marks the rapid appearance of large animal skeletons
• The Phanerozoic Eon shows a large biodiversity curve for genera
• Five major mass extinction events occurred at the Family Level

Cambrian Fauna

• Though diverse, Cambrian Fauna occupied a narrow range of seafloor habitats
• Most Cambrian Fauna were sessile or immobile
• There was a major increase in diversity during this period
• Mobile forms were mostly deposit feeders or grazers
• They lived on shallow continental shelves

Decline of Soft-Bodied Animals

• Soft-bodied animals and stromatolites declined sharply
• Decline possibly caused by the appearance of predators and grazers
• Modern stromatolites are found in sharks bay, Australia
• They survive where others cannot because they can tolerate air exposure

Paleozoic Faunas

• Paleozoic Faunas saw a Mid-Ordovician expansion of marine habitats
• Habitats were still limited to shallow marine shelves
• This led to the greatest diversification in marine history
• Important faunal changes began

Life on the Ordovician Seafloor

• Vertical habitats were utilized, such as bivalves burying in the mud
• The first skeletonized reef buildups appeared
• Crinoids (sea lilies) were also present

Post-Cambrian Animal Trends

• A predator-prey “arms race" began
• Predators became more efficient, leading to prey developing more protection
• Diversification of successful groups occurred
• Habitats expanded vertically
• Anatomical advancements arose

Examples of Animals - Predators

• Ordovician straight-shelled nautilus existed
• Modern nautilus is still around today and still has good eyes
• Silurian sea scorpion lived in coastal areas, and grew larger than a 6ft human
• Starfish share the same phyla as crinoids
• Starfish use their arms to pry open clams

Examples of Animals - Prey

• Clam-like brachiopods underwent mass expansion
• Brachiopods started slow in the cambrian period
• Strong shelled brachiopods had mass expansion in the ordovician
• Early brachiopods had thin, fixed shells
• They eventualy developed thick, hinged shells in the mid-paleozoic period and were quite successful
• Trilobites rolled up for protection in the Devonian Era
• Trilobites had hard outer shells, and are were fossilized by landslides

Burrowing

• Burrowing became more common
• Sedimentary rocks show disruption of layering in seafloor sediments
• Burrowing activity increased from the Cambrian to Ordovician periods

Tiering

• Habitats expanded above and within the seafloor
• This expansion included growing upwards and burrowing downwards
• Tiering especially seen in crinoids
• When they die, crinoids break down into skeleton pieces

Seafloor and Reefs

• Clams burrowed into the seafloor
• Colonial corals and calcareous sponges made large, vertical CaCO3 reef structures
• These structures were strong and wave-resistant
• Reefs followed the vertical expansion of habitats
• Succession and zonation occurred
• Bryozoans closely resemble corals with with individual organisms living together
• Bryozoans are know as "lace animals"

Trilobites Over Time

• Trilobites originated in the Cambrian
• As the Paleozoic progressed, they became more complicated
• They developed bigger sensory organs in the head as well as compound eyes
• All this occurred within the phonic zone

Paleozoic Faunas

• Paleozoic faunas' diversity "plateaued" for about 200 million years
• To avoid crowding, animals tiered
• Shallow shelf habitats were susceptible to environmental change
• Alterations in sea level affected shallow water communities
• These communities affected by temperature changes, regression, and transgressions
• The sea level changes on the shelves was problematic

Late Ordovician Period

• Climate change and glacier buildup led to massive extinction
• Large continental mass over the south pole promoted the build up of ice sheets
• Global cooling trapped water in ice, causing the sea level to fall substantially
• This regression exposed shelves and caused the first major mass extinction

Extinction Events

• Fewer extinction events happened over time
• Major extinction removes unsuccessful survival attempts and makes room for the successful

Victims of Ordovician Extinction

• Over 50% of marine genera spread over about 100 families from several different groups
• Extinction happened in two “pulses"
• First pulse occurred when glaciers expanded, hitting tropical communities hard
• Cooler water species migrated to the poles
• The creatures that adapted, survived
• The second extinction pulse occurred when glaciers melted
• Cooler water species suffered during warming

Microbial Mats

• Microbial mats expanded, coating the seafloor due to the absence of grazers
• Many hard-hit groups in the extinction re-diversified
• More mollusks and clams appeared
• Trilobites never recovered

Late Devonian Mass Extinction

• Late devonian mass extinction was related to the buildup of glaciers and sea level lowering
• Boundaries between eras mark changes in fossils, a result of extinction
• Global cooling linked to the initial Devonian expansion of land plants
• Carbon dioxide levels dropped due to increased chemical weathering from roots
• Global cooling was tied to plant activity
• Plants had a (greenhouse influence on climate change in the past)
• Devonian victims included around 40% of marine genera
• They included all stromatoporoids, all shallow water stoney and rugose corals
• New families evolved later, and most trilobites such as the phacopids died

Paleozoic Life - Vertebrates

• This information is dated March 11th, 2025, and refers to a 300 Ma Period
• The oldest known Chordate is the Pikaia, from the Middle Cambrian Burgess Shale
• Phylum Chordata includes Subphyla Urochordata, Cephalochordate, and Vertebrata

Chordate Characteristics

• Chordates have a notochord that prevents accordion locomotion
• They feature segmented muscles for locomotion
• Chordates have a dorsal nerve cord and a Pharynx (Throat) with “gill slits”
• They also have a post-anal tail
• Some creatures display "Neoteny", or holding onto youth, and retain juvenile features

Tunicates / Sea Squirts

• Tunicates, or Sea Squirts are sessile
• They occupy Urochordata
• Chordates evolved from the tunicate larva by early sexual maturation, this is a common evolutionary pattern
• Chordates came from the larva of a sea squirt

Cephalochordate

• Cephalochordate are adults with a notochord
• They are exemplified by the lancelet
• Lancelets filter feed on the seafloor
• The Pikaia is the first known cephlochordate

Fish - Earliest Vertebrates

• The earliest fish appeared in the Ordovician
• They were jawless fish, or Agnathta, with teeth on their lips and tongues
• They possessed platy body armor

Agnathids

• Early Agnathids were bottom-feeding mudsuckers
• The modern jawless hagfish
• Jaws evolved from flexible bones of jawless fish
• These bones were originally used to open gill slits
• This adaption aided respiration, and biting came later

Jawed Fish Groups

• Placoderms were an extinct group of armored fish
• Placoderms featured a cartilaginous skeleton
• Armored fish of the Paleosoiz grew up to 10 m in length
• Chondrichthyes includes cartilaginous fish (sharks and rays)
• The fossil record is limited, and cartilage is not reserved, but their teeth are
• Osteichthyes are a class, and include bony fish and float bladder (ray and lobe finned fish)
• Bony fish are the most successful vertebrates
• There are 40,000 living species of bony fish

Bony Fish Groups

• Ray-finned fish
• Lobe-finned fish

Devonian Lobe-Finned Fish

• Devonian lobe-finned fish were jawed, and there were many in greenland
• There was also australian lungfish, coelacanth (modern lobe-finned fish thought to be extinct)

Fish Out of Water

• Bones and muscles of lobe fins could support the weight of the fish
• Lungs were a modified float bladder, that evolved before legs

Amphibians

• Amphibians are fish out of water
• Amphibians reproduce by laying eggs in water with, external fertilization
• Some amphibians develop through an aquatic juvenile stage called tadpoles
• Breathing is done through lungs that already evolved from the float bladder
• Fluid retention happened through mucous glands that became oil glands in skin
• Locomotion happened through early limbs modified into walking legs
• Amphibian eggs have no shells

Lobe Fin Fish

• There are many similarities between lobe fin fish and amphibian limbs
• Tiktaalik is a missing link between lobe-finned fish and amphibians
• Tiktaalik, which is an inuktitut word for “burbot", was a freshwater fish with fingers
• Tiktaalik was discovered by Neil Shubin
• Key features of Tiktaalik include a flexible neck and wrist bones, but could not run around
• The first actual amphibians appeared in the Mississippian Period

Reptiles

• Reptiles did not have to return to water to reproduce
• They first appeared in the Pennsylvanian, at the same time as the coal swamps
• Their skeletons were similar to those of amphibians

Amniotic Egg

• The Amniotic Egg was a gateway to land
• Amniotic Eggs had a hard, protective shell able to regulate temperature
• Amniotic Eggs are porous to allow gas exchange and respiration
• Amniotic Eggs have a nutritive sac to feed the embryo
• They required internal fertilization to remove environmental influence

Permian Reptiles

• Permian reptiles included Pelycosaurs
• Pelycosaurs are fin-back reptiles, and aren't dinos
• Their jaw was similar to later mammals
• Latest Permian included therapsid reptiles
• Therapsid reptiles had legs under their body making them more active
• Their teeth were more specialized than pelycosaurs
• They likely regulated body temperature like mammals

Permian Mass Extinction

• Occurred at the end of the Permian or end Paleozoic periods
• This was the largest biotic crisis in Earth's history, with 2 "waves of extinction"
• 60-80% of genus/species went extinct
• This was called the END of ancient life

End-Paleozoic Extinction Details

• Marine life suffered a genera loss of 60%, with species losses reaching 80%
• Most bryozoans, brachiopods, crinoids, and cephalopods died
• Nearly all paleozoic corals went extinct
• All remaining trilobites died as well
• This was the first mass extinction of vertebrates on land as well
• Almost 80% of amphibians and reptiles died

Hotly Disputed Topics

• How much did Volcanoes contribute
• How much did Glaciers (late paleozoic ice age) contribute
• How much did the Formation of pangaea contribute
• How much did Extraterrestrial impact contribute

Deep-Sea Deposits

• Permian deep-sea deposits record changes in oxygen levels
• Black shale interval found in Japan

Deep-Sea Interval Details

• Oxygen at the bottom of the sea is required to oxidize ions
• Dark Gray/Black shales require low oxygen to form
• Black shales mean organic matter did not oxidize
• From mid to late permian, oceans had low oxygen conditions extending onto continental shelves
• Oceans were stratified
• The likely cause was greenhouse warming
• The warming related to the largest flood basalts (lavas) in the phanerozoic
• Large eruptions during the permian occurred in siberia and china: siberian traps
• Radiometric dates of large flood basalts coincided with the two extinction phases
• Large Massie releases of CO2 produced by the eruptions warmed the earth
• Volcanism released great quantities of greenhouse gasses
• This caused warmer global temperatures, and stratification of the ocean
• Pangaea may have exaggerated the extinction

Pangaea effects

• Continental shelves are minimized when continents are locked together
• This caused MAJOR habitat loss
• Sea floor spreading slowed down when all continents locked together
• This led to sea floor cooling and subsidence of oceanic lithosphere
• Pangaea led to major regression of sea level fall

Origins of Petroleum

• The fossil fuels we previously covered include coal
• The recipe for fossil fuels is as follows:
• Organic carbon
• Preserved organics prior to burial by lack of oxygen
• Rapid burial to transforms organics into fossil fuels

Petroleum Definitions

• Liquid hydrocarbons (or oil)
• Any fluid hydrocarbon compound that includes liquids and gasses
• Petroleum is NOT made of the remains of dinosaurs

Petroleum Formation

• They lived on land
• When they die, they decompose in the presence of oxygen and scavengers
• They also are not big enough
• Petroleum is mostly algae and bacteria
• Photosynthesizers (phytoplankton) are floaters
• When they die, they sink

Shale Formation

• Organic material joins with fine grain sediments, like silt, and clay
• This materials is then buried with more mud
• The mud helps to preserve the organics by sealing them off from O2
• Most of the grains in muds are plates, and therefore stack
• This stacking causes shales and mudrocks to to be weak
• In brown mud at the surface, organics have oxidized
• Below the top layer, organics are sealed below the ground, differentiated by a darker color
• When organic-rich black mud lithifys, it gets black shale
• Not all shales contain enough organics, but the ones who do are called source rocks
• Source rocks are shales with enough organics to produce petroleum
• Permian black shale was deposited during the extinction
• Black shales require low oxygen conditions to form
• Warm and stratified permia's oceans
• Surface waters get oxygen from the atmosphere, but decrease the deeper you go

Acadian Orogeny

• The acadian orogeny was the 2nd Appalachian tectonic event
• The Acadian orogeny of middle to late devonian
• Organics preserve in the catskill foreland basin
• Acadian mountains provide the sediment
• The Catskill Delta: Acadian deposition
• Marcellus Shale is a special black shale
• Middle Devonian is characterized by widespread black shale deposition
• The Devonian period was a-"Greenhouse (no major ice sheets) Earth"
• There were Greenhouse vs. Icehouse periods
• Warm temperatures led to higher sea level and more epicontinental seas
• The Catskill Foreland Basin was 20 - 30 degrees south
• The Acadian Orogeny occured in the Middle Devonian
• There were Tropical latitudes and plenty of sunshine
• Lots of happy marine plankton lived near the surface with lots of dead plankton on the bottom
• Lots of organic material was suitable for oil and gas formation
• Rain shadow from easterly trade winds reduced runoff/clastic influx, causing low sedimentation rates in the basin

Warm Basin

• The basin was a warm shallow sea
• The Earth was warm during this period, so there wasn't as strong of circulation

Oxygen Concentration

• Oxygen concentrations became limited in a restricted basin
• Oxygen levels dropped when limiting vertical circulation
• Low oxygen leads to the preservation of organics
• Marcellus Shale's high organic content only needs 1% of material organic to turn shale black, but has 10%
• Mud becomes shale, and this traps ANY fluids
• This gives the rock the property of high porosity and yet low permeability

Unconventional Resources

• Unconventional resources include shale oil and gas
• Petroleum firms use this method because they don't have to rely on migration and traps

Unconventional Extraction

• Petroleum companies employ “unconventional” technologies
• Directional drilling is one such method
• It permits access to more of the source rock, and allows companies to drill from a central point

Hydraulic Fracturing

• Hydraulic fracturing creates artificial permeability
• This allows petroleum to flow out of source rocks for recovery
• Conventional drilling is the process of drilling into traps to recover petroleum

Petroleum Traps

• Petroleum traps are accumulations of oil and gas
• Petroleum seeps out and migrates upwards through reservoir rocks
• This migration continues until it is blocked by a sealing layer

Conventional Resource Ages

• 20% are cenozoic
• 70% mesozoic
• 10% paleozoic

Mesozoic Paleography

• Restricted seaways were features of the jurassic period
• When buried, salt floats upwards because its lower density
• These salt deposits form salt domes

Petroleum Reservoirs

• Petroleum Reservoirs are often located in reefs
• These areas feature Equatorial circulation with warm water
• This is a process that promotes high organic productivity
• This circulation coincided with the expansion of phytoplankton in the cretaceous

Stratified Tethys Ocean

• The cretaceous the Stratified Tethys Ocean
• The stratification pattern today shows cool water sinks, and carries O2 to deep water
• Creaceous stratified warm seas so low O2 layers would expand
• This pattern caused Organic rich mud to accumulate

Mesozoic Recovery

• The mesozoic recovery saw the paleozoic corals replaced by hexacorals
• Coral reef limestones made good petroleum reservoirs
• Closure of the tethys began, leading to Cenozoic orogenic belts

Cenozoic Belts

• Cenozoic orogenic belts result from continental collisions
• These zones created lots of deformed rocks
• Persian gulf region, fold and fault traps
• Nearly half of the world's conventional oil is in the persian gulf region

Coopers Rock State Forest

• Overlook, which has a view of the Cheat River
• Situated on Chestnut ridge, where greens are lower elevation, and reds are higher
• Allegheny Mountain Section
• Boundary: Separates the low plateau (most of western west virginia) and the high plateau (the Allegheny Mountain Section) where Cheat River is
• Morgantown is "Low Plateau" where all areas are relatively the same height
• "High Plateau" is Chestnut ridge which has about 1000 feet of elevation change

Plateau Folds

• The Low Plateau is made up of very gentle folds
• There are mostly soft shales, of the Upper Pennsylvanian Rocks found in the Low Plateau
• The High Plateau has tighter folds and more dip
• The High Plateau also has mostly soft shales Upper Pennsylvanian Rocks , but with a distinct location
• Middle Pennsylvanian Rocks (dark green)
• The Plateau has more sandstone
• Pottsville sandstone dominates the surface of Cooper’s rock
• Patches of younger Allegheny and older mauch chunk (the sandstones of Cooper’s rock is in this unit)
• Most of Morgantown is Conemaugh

Pottsville Formation

• 3 members of sandstone makeup the Pottsville Formation
• Homewood sandstone
• Upper Connoquenessing sandstone, which contains most of the sandstone cliffs and blocks
• Lower Connoquenessing sandstone

Cooper’s Rock

• Cross Bedding can be seen on Cooper’s rock
• This is how the scientist can interpreate the direction that one way rivers where flowing
• The rivers were flowing in the same direction
• Braided streams exist, and plant fossils show up from deposits
• One could see stress fractures or Joints
• One can see in the outcrop belt; natural pattern of joints from the sandstone
• The stress is perpendicular to the chestnut ridge fold axis
• Joint sets (Yellow): 1 perpendicular, 1 parallel.

Mesozoic Life

• What characterizes the Mesozoic: widespread dry red beds
• Opening of the atlantic seaway: gondwanaland separates
• Late permian: therapsid reptiles had legs under body for active and fast movement
• Permian reptiles had teeth were specialized compared to the pelycosaurs
• In the Permian period they likely regulated body temperature like mammals

Mesozoic Era

• Also known as the age of reptiles
• Triassic reptiles that transitioned to the marine realm include:
  • Placodont
  • Nothosaur
  • Plesiosaur
  • Mosasaurs
  • Ichtyosaur
    • this was new in this period, the first instance when animal birth was live
• Synapsids: gave rise to mammals
• In the dino branch: jurassic crocodile
  • Evolved in terrestrial habitats, moved into marine habitats
    • The evolved speices was Sarcosuchus

Flying Reptiles

• Pterosaurs include: winged lizards
• Pterosaur flyers, have wings are different from birds or flying mammals
• A key difference is extension of the pinky digit supporting the wing

End Triassic Mass Extinction

• Along with other large amphibian and reptile groups
• Therapsid reptiles experienced major extinctions
• Dinosaurs were able to survive and rose to prominence
• Break up of Pangea and Greenhouse gas emissions were prominent, as Rifting generated extensive volcanism
• Absolute ages match timing of extinction
• Co2 and temperature increases recorded in plant tissues confirm greenhouse warming
• Dinos are perceived as
  • Old idea: slow, lumbering giants who were the ancestors of large reptiles
  • New: dinos were more active as we know that birds came from dinos
• Early dinosaurs: dinosauromorphs were
  • Small and active predators, with a bipedal upright stance

Dinosaur vs. Reptiles

• Dinosaur has Dino: upright stance (triceratops)
• While reptiles (Non dino) have a sprawling stance (dimetrodon)
• Sauropods can be thought of as the old view of dinosaurs

Dinosaur Branches

• Two major branches of dinosaurs:
  • Ornithischia
    • Herbivores that live in land habitats
  • Saurischia
    • Can be can be mix of herbivores or carnivores
    • They led to the evolution of birds

Dinosaur Anatomy

• The Dinosaur pervic structure
  • sauriscian: lizard hipped
  • Ornithischia has bird hipped like the therapods

Sauropods Anatomy

• Sauropod tracks reveal that these animals moved about in heards with no tailmarks
  • How could they eat enough eating fossil and modern cycads (palm tree like plants)
    • Answer: eating with Gizzards and with the help from rocks
  • These could have been gigantotherms
• The very first theropod to arrive on the hunting scene: allosaurus that was the precursor to the cretaceuous T. Rex

Raptors

• Raptors were Feathered, with 3 toed that suggest long strides
• What suggest that therapods were warm blooded was the presence of Feathers
• Dinosaur eggs could be found in Patagonia
• Dinos nested with eggs arranged but only half buried